1. Field of the Invention
The present invention concerns improvement in the skid rail of furnaces used in, for example, steel industry for heating steel pieces.
2. State of the Art
As the material for preparing skid rails of heating furnaces such as walking beam furnaces or pusher furnaces, heat-resistant casting alloys have been used. In the soaking zone of a furnace, the skid rails are subjected to such a high temperature as 1200.degree.-1350.degree. C., and suffer from heavy strain and abresion, and therefore, the libes of the skid rails are short.
It has been proposed to use ceramics having high heat-resistant and anti-abrasion properties as the material of the skid rails or skid buttons (for example, Japanese Utility Model Publication No. 35326/1980), and the assignee has made efforts in improving the material (for example, Japanese Patent Disclosure No. 89516/1985).
So-called fine ceramics materials such as SiC and Si.sub.3 N.sub.4 preferable from the view point of high shock-resistance thereof, which is one of the properties requested to the skid rails, are easily damaged by oxidation when used in a strongly oxidative atmosphere. On the other hand, research has been made since few years ago on the super alloys of oxide-dispersion reinforced type, i.e., Ni-based super alloys in which fine particles of an oxide having a high melting point such as Y.sub.2 O.sub.3 are dispersed, and application thereof to gas-turbines and jet-engines has been tried (for example, Japanese Patent Publication No. 38665/1981). As to high temperature furnace it has been proposed to use an oxide-dispersion reinforced type super alloy of the composition consisting of 12.5-20% Cr, up to 1% Al, up to 0.1% C and up to 0.5% (volume) Y.sub.2 O.sub.3, the balance being Ni, as the material for mesh belts (Japanese Patent Publication No. 9610/1984).